The present invention generally relates to cutting tools and, more particularly, to the connection of rotary cutting tools to spindles.
Recently, a new interface between a rotary cutting tool and a spindle adaptor was developed seeking solutions to various problems relating to interfaces utilizing a steep angle taper and/or long taper. Particularly improvement was desired with regard to static and dynamic elasticity, tool change precision, and deformation at high speeds. As a result of this development, DIN standard 69893 issued which is directed to the dimensional relationships of a hollow short taper shank of a cutting tool and an associated recess in a spindle adapter. The DIN standard, however, does not address the structure or operation in which the tool shank can be gripped or expanded from its interior to press the shank against the mating recess of the adaptor.
A number of cutting tool manufacturers have developed different clamping or locking mechanisms for this interface between the cutting tool and the spindle adaptor. Each manufacturer secures the lock mechanism to the spindle adaptor within the tapered recess. Typically, the clamping mechanism includes a series of projections or fingers which can be selectively moved radially inward and outward. Once the tapered shank of the cutting tool is properly positioned within the tapered recess of the spindle adaptor, an actuating screw of the clamping assembly provides radial movement of the fingers. Rotation of the screw in one direction moves the fingers radially outward into engagement with the internal surface of the shank hollow interior within an internal groove to form an interference in the longitudinal direction.
When tool changeover is required, rotation of the actuator screw in the other direction retracts the fingers radially inward to remove the interference so that the cutting tool shank can be removed. The lock mechanism remains in place in the tapered recess of the spindle adaptor, making the tapered recess into a narrow annular recess. A new cutting tool shank is then inserted into the tapered recess of the spindle adaptor over the lock mechanism and the same process is followed to secure the cutting tool to the spindle adaptor.
While this interface may be an adequate solution for some cutting tool applications, particularly CNC machining centers, the interface may pose additional problems for other cutting tool applications, particularly dedicated spindles. One problem relates to the internal groove which has tolerances which are very difficult to maintain. As a result, the tool is very difficult and expensive to produce. Unfortunately, this internal groove tolerancing is only for the purpose of clamping the cutting tool. There is also some question as to the strength of the narrow wall thickness at the location of the internal groove.
Another problem relates to cleaning. It is of primary importance that the mating, tapered surfaces of the spindle adapter recess and the cutting tool shank be kept clean. Any chips from the cutting operation that become lodged in the recess must be removed. The known lock mechanisms limit accessibility to the tapered recess in the spindle adapter as described above since the lock mechanism is mounted and retained therein. This is particularly a problem in dedicated spindle applications such as transfer line, dial, and trunion line machines which generally require manual tool changing and frequently have limited visual and physical access thereto. With the clamping mechanism located in the female end, it is virtually impossible to clean the spindle adaptor recess. Operators cannot get their fingers inside to wipe the female socket. Chips, dirt, and coolant with small metal filings will most certainly freeze the clamping mechanism, making it impossible to remove the cutting tool. It is not practical to develop inside air blast cleaning for manual installations and external air blasts throw the chips back into the mechanism. Accordingly, there is a need in the art for an improved cutting tool interface.